Show instruction when logging join

[folex]

Right now, joins look like this

[2022-04-02T21:17:58.595125Z INFO  aquamarine_0.21.3.wasm]   waiting for an argument with idx '0' on stream with size '0'
[2022-04-02T21:17:58.595137Z INFO  aquamarine_0.21.3.wasm]   waiting for an argument with idx '0' on stream with size '0'
[2022-04-02T21:17:58.595140Z INFO  aquamarine_0.21.3.wasm]   waiting for an argument with idx '0' on stream with size '0'

For big AIR scripts, it's really hard / impossible to guess which line caused this. Printing instruction as in last_error.instruction would help a lot.